Understanding the Consequences: When a person takes in more energy than they need?

October 31, 2025 •

4 min read

According to the World Health Organization, the worldwide prevalence of obesity has increased dramatically, posing a serious threat to human health. This happens precisely when a person takes in more energy than they need, causing a sustained positive energy balance that results in the body storing the excess calories, primarily as body fat.

Quick Summary

This article explains the metabolic fate of excess calories, detailing how the body stores surplus energy as glycogen and then as fat. It covers the short- and long-term health risks of chronic overconsumption, including weight gain and chronic diseases. Strategies for achieving and maintaining energy balance are also explored.

Key Points

Positive Energy Balance: Consuming more calories than the body burns leads to weight gain and fat storage.
Glycogen Storage: Excess carbs are first converted and stored as glycogen in the liver and muscles for short-term energy.
Fat Storage: Once glycogen stores are full, surplus calories are efficiently converted and stored as body fat (adipose tissue) for long-term energy.
Health Risks: Chronic positive energy balance increases the risk for serious conditions like heart disease, type 2 diabetes, and certain cancers.
Managing Excess Calories: Achieving a negative energy balance requires a combination of reduced calorie intake through diet and increased energy expenditure via physical activity.
Beyond Physical Effects: Significant psychological consequences, including depression and anxiety, can also result from weight gain and obesity.

The Core Principle of Energy Balance

At its heart, weight management and overall nutritional health are governed by the principle of energy balance. This balance is a simple equation: energy in versus energy out. Energy 'in' comes from the food and beverages we consume, measured in calories ($kcal$). Energy 'out' is what the body burns for its basic functions, for digesting food, and for physical activity. When energy intake consistently exceeds energy expenditure, a state of positive energy balance exists. Conversely, a negative energy balance occurs during weight loss, while equilibrium maintains a stable weight.

Short-Term Effects: From Glycogen to Fat

Initially, when a person consumes excess carbohydrates, the body’s first response is to store the surplus glucose as glycogen. This polysaccharide is stored primarily in the liver and muscles and acts as a readily accessible, short-term energy reserve. A typical adult can store approximately 450 grams of glycogen in total.

However, glycogen storage capacity is limited. The liver can hold about 80-100 grams, and muscle cells can store around 300 grams. Once these glycogen stores are full, the liver initiates a process called lipogenesis, converting the remaining excess carbohydrates and other macronutrients into fatty acids. These fatty acids are then transported throughout the body and stored as body fat, or adipose tissue, in fat cells.

The Body's Preference for Fat Storage From an evolutionary standpoint, the body's efficient storage of fat is a survival mechanism honed over millennia of feast-or-famine cycles. Fat is a highly efficient energy storage medium. It is more calorically dense than carbohydrates, providing about 9 calories per gram compared to 4 calories per gram for carbohydrates. Furthermore, fat tissue contains very little water, unlike glycogen, which is heavily hydrated. This makes fat a compact, long-term energy reserve.

Long-Term Consequences: The Health Risks

Chronic positive energy balance, or sustained overconsumption of calories, has serious and far-reaching health implications. The accumulation of excess body fat can lead to a cascade of metabolic and physiological issues.

Cardiovascular Disease: Excessive weight puts a strain on the heart and can contribute to high blood pressure, unhealthy cholesterol levels, and inflammation, all of which are risk factors for heart disease and stroke.
Type 2 Diabetes: Increased body fat, particularly visceral fat around the abdomen, can lead to insulin resistance. This means the body's cells don't respond effectively to insulin, leading to high blood sugar levels and eventually, type 2 diabetes.
Mental Health Issues: The psychological effects of sustained weight gain are significant. Individuals may experience depression, anxiety, low self-esteem, and body image dissatisfaction, which can create a negative feedback loop of emotional eating.
Metabolic Syndrome: This is a cluster of conditions that includes increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels. Having metabolic syndrome increases the risk of heart disease, stroke, and diabetes.
Certain Cancers: Obesity is a known risk factor for several types of cancer.
Musculoskeletal Problems: The physical stress of carrying excess weight can damage joints and lead to conditions like osteoarthritis.

Addressing the Calorie Surplus

Counteracting a positive energy balance involves two main components: reducing calorie intake and increasing energy expenditure. A comprehensive strategy for weight management should address both. Mindful eating and informed food choices are fundamental.

Here are some actionable steps:

Portion Control: Be aware of serving sizes, especially when dining out, where portions have dramatically increased. Using smaller plates can also help manage intake.
Focus on Nutrient-Dense Foods: Prioritize vegetables, fruits, whole grains, and lean proteins, which are more satiating and nutrient-rich than highly processed foods high in sugar and fat.
Increase Physical Activity: Regular exercise is crucial for burning calories and supporting overall health. The Centers for Disease Control and Prevention recommends at least 150 minutes of moderate-intensity aerobic activity per week, plus two days of muscle-strengthening activities. Activities like walking, jogging, cycling, and strength training all contribute to energy expenditure.
Mindful Eating: Paying attention to the process of eating—savouring flavours, eating slowly, and listening to fullness cues—can help reduce overconsumption.
Stay Hydrated: Drinking plenty of water can help with fullness and may prevent the body from confusing thirst with hunger.

Comparison Table: Glycogen vs. Fat Storage


Feature	Glycogen	Fat (Adipose Tissue)
Storage Capacity	Limited (approx. 450g)	Virtually unlimited
Storage Location	Liver and muscles	Throughout the body, particularly in adipose tissue
Energy Density	Lower ($4$ kcal/g, with water)	Higher ($9$ kcal/g, little water)
Water Content	High	Very Low
Accessibility	Rapidly mobilized for quick energy needs	Slower mobilization, reserved for long-term energy needs
Evolutionary Role	Short-term energy reserve for immediate use	Long-term energy reserve for periods of food scarcity

Conclusion

When a person takes in more energy than they need, the body has a highly efficient system for storing that excess. While this mechanism was a survival advantage for our ancestors, in modern society, where calorie-dense foods are plentiful and physical activity is often low, it contributes to widespread issues of overweight and obesity. Understanding this fundamental aspect of metabolism is the first step toward regaining control. By balancing calorie intake through mindful eating and portion control with increased physical activity, it is possible to counteract a positive energy balance and mitigate the associated long-term health risks. A sustainable approach focuses not on extreme restriction, but on consistent, healthy habits that promote overall well-being.

Visit the Centers for Disease Control and Prevention for more information on managing a healthy weight.

Frequently Asked Questions

The body first stores excess glucose as glycogen. Once glycogen stores are full, the liver converts any remaining excess into fatty acids for long-term storage, a process that can begin relatively quickly after a large meal.

Yes. The body can convert excess carbohydrates and protein into fat for storage. A diet high in added sugars, for example, can contribute significantly to weight gain even if fat intake is limited.

Glycogen is a short-term, readily available energy source stored with a lot of water, making it less energy-dense. Fat is a long-term, highly concentrated energy reserve that the body uses when immediate glucose is not available.

Physical activity increases the body's energy expenditure, which helps to create a calorie deficit. It can also improve metabolic rate, build muscle, and use up stored glycogen and fat for energy.

Yes, carrying excess weight can lead to mental health issues such as low self-esteem, depression, and anxiety. Societal stigma and the physiological effects of obesity can also exacerbate these psychological challenges.

An occasional over-the-top meal is unlikely to cause lasting weight gain. The body will prioritize using or storing the excess energy in the short term. The issue arises when overeating becomes a frequent habit.

Metabolic adaptation is when the body's energy expenditure changes in response to changes in energy intake. During periods of overfeeding, some individuals experience a slight increase in metabolism, but this is highly variable and usually not enough to prevent weight gain.